Dual voltage transformer switch



Nov. 22, 1966 E. J. LEHMAN Y DUAL VOLTAGE TRANSFORMER SWITCH 5 Sheets-Sheet 1 Filed March 9, 1965 INVEN TOR.

,5 BY U567??? Nov. 22, 1966 E. J. LEHMAN 3,287,510

DUAL VOLTAGE TRANSFORMER SWITCH Filed March 9, 1965 5 Sheets-Sheet 2 INVENTOR. 5056/76 J Lehman i2, A M) fittorrxgr NOV. 22, 1966 J M N 3,287,510

DUAL VOLTAGE TRANSFORMER SWITCH Filed March 9, 1965 5 Sheets-Sheet 5 INVENTOR. Eugene J Lehman flttormsy United States Patent 3,287,510 DUAL VGLTAGE TRANSFORMER SWITCH Eugene J. Lehman, Zanesville, Ohio, assignor t0 McGraw- Edison Company, Milwaukee, Wis., a corporation of Delaware Filed Mar. 9, 1965, Ser. No. 438,265 15 Claims. (Cl. 200-6) This invention relates to electrical switches and, in particular, to high voltage switches for changing transformer connections.

This invention is an improvement over the dual voltage transformer switch disclosed in my copending application Serial No. 157,349 filed December 6, 1961, now Patent Number 3,177,305.

Dual voltage switches for electrical power distribution transformers permit an electrical utility to change a transformer from a lower voltage rating to a higher voltage rating, and thus eliminate the end for replacing the transformer, if the power distribution system is converted to a higher voltage. The transformer winding may comprise a plurality of sections, and the voltage rating of the transformer may be varied by changing the winding sections between series and parallel. A dual voltage switch, which is sometimes referred to as a series multiple switch, allows connecting the winding sections in series or in parallel and thus permits operation of the transformer on either of two voltages, for example, 1200 or 2400 volts.

Known dual voltage switches have wiping type contacts which do not provide sufficient contact pressure at the higher transformer kva. ratings to meet the standards of the National Electrical Manufactures Association (NEMA) which require that the switch carry rated transformer current continually and also carry short circuit current of up to twenty-five times rated current for a predetermined period of time. My aforementioned application Serial No. 157,349 discloses a dual voltage switch having sufficiently high contact pressure to carry currents well in excess of the magnitudes specified by NEMA standards for transformers up to 167 kva. and 18 kilovolt rating and yet is operable between positions with minimum torque. One disadvantage of the switch of my copending application is that it requires a separate slave switch when changing transformer voltage ratios in multiples other than integers, for example, from 2400 to 7620 volts.

It is an object of the invention to provide a transformer dual voltage switch which is much more compact than prior art switches of similar voltage and kva. rating and is capable of changing transformer voltages in either integer or non-integer ratios. It is a further object of the invention to provide such a compact dual voltage switch having sutiiciently high contact pressure to carry currents well in excess of the minimum magnitudes specified by NEMA standards and yet is operable between positions with minimum torque and has means to positively break apart the stationary and movable contacts if they become welded together as a result of excessive overload. Still another object of the invention is to provide such a compact dual voltage switch having novel actuating means to assure that the movable switch contact has been fully moved into the other switch position and does not hang up between switch positions.

These and other objects and advantages of the invention will be more readily apparent from the following detailed description when taken in conjunction with the accompanying drawing wherein:

FIG. 1 is a circuit diagram illustrating typical switching connections completed by the dual voltage switch of the invention to alternately connect transformer winding sections in series and parallel and thus change voltage in integer ratios;

FIG. 2 is a circuit diagram similar to FIG. 1 but illus- "ice trating typical switching connections completed by the switch of the invention to change transformer voltage in non-integer ratios;

FIG. 3 is a sectional view taken along the axis of the operating shaft of the preferred embodiment of the invention when the switch is in the parallel position;

FIG. 4 is a view taken along line 44 of FIG. 5;

FIG. 5 is a view taken for one end of the switch of FIG. 3;

FIG. 6 is a view taken on lines 6-6 of FIG. 3;

FIGS. 7 and 8 are views taken from the opposite end of the switch with the operating cap respectively in place and removed;

FIG. 9 is a partial view taken through the switch actuating means with the cap removed and showing the latch in full lines in the locking position and in dotted lines in the released position;

FIG. 10 is a view taken on line 1010 of FIG. 9; and

FIG. 11 is a partial sectional view taken diametrically through the axis of the switch operating shaft and showing the position of the movable contact carrying member when being actuated between series and parallel positions;

The dual voltage, or series-multiple, switch 10 of the invention is adapted when in a first position to connect three transformer primary winding sections ab, cd, and e shown in FIG. 1 in parallel and when in a second position to connect these three winding sections in series in order to change the transformer from one voltage ratio to a higher one, or vice versa. The dual voltage switch 10 has two sets of four stationary contacts E, A, C, G and H, B, D, F arranged in a circle. Contacts E, A, C and B, D F are individually connected by wire leads 11 to correspondingly lettered ends of the three transformer primary winding sections ab, cd, and ef so that one end of each winding section is connected to a stationary contact of one set E, A, C, G and the other end is connected to a stationary contact of the other'set H, B, D, F. For example, end a of winding section ab is connected by a lead 11 to a stationary contact A of set E, A, C, G and end b of this winding section ab is connected by a lead 11 to a stationary contact B of set H, B, D, F. The conductors 12 of an alternating current power system are connected to the stationary contacts A and D. Stationary contact G is connected by a jumper wire 14 to stationary contact C, and stationary contact H is connected by a jumper wire 15 to stationary contact B.

The movable contact assembly of switch 10 carries two arcuate metallic movable contacts 17 and 18 adapted, when the switch 10 is in the full line parallel position shown in FIG. 1, to respectively common three stationary contacts E, A, C of one set and three stationary contacts B, D, F of the other set, whereby the three electrical coil sections ab, cd, and ef are connected in parallel. In the second, or series, position wherein the arcuate contacts 17 and 18 are shown in dotted lines, the movable arcuate contacts 17 and 18 are adapted to respectively common the stationary contacts E and H and the stationary contacts G and F, whereby the three winding sections are connected in series in a circuit which may be traced from one power line lead 12 to stationary contact A, winding section ab, stationary contact B, jumper wire 15, stationary contact H, elongated movable contact 17, stationary contact E, winding section ef, stationary contact F, elongated movable contact 18, stationary contact G, jumper wire 14, stationary contact C, winding section cd, and stationary contact D to the other power line lead 12. It will be appreciated that the dual voltage switch of the invention, when wired in accordance with the schematic diagram of FIG. 1, is capable of changing the voltage ratio of the transformer in the integer ratio of 3 to 1. For example, if each winding section ab, cd and ef were of 2400 volts, operation of the switch would change the primary winding voltage between 2400 and 7200 volts.

The switch of the invention is adapted to change the transformer voltage ratio in non-integer multiples, for example, 2400 to 7620 volts, when connected in accordance with the circuit diagram of FIG. 2 which is similar to that of FIG. 1 except that the jumper wires 14 and 15 are omited; one 2610 volt winding abh is provided having a 2400 volt tap at b connected to stationary contact B and the winding end h connected to stationary contact H; and a second 2610 volt winding dcg is provided having a 2400 volt tap at 0 connected to stationary contact C and the winding end g connected to stationary contact G. When the switch is in the full line paralle position, the movable arcuate contacts 17 and 18 respectively common the three stationary contacts E, A, C and the three stationary contact B, D, F to parallel the three winding sections ab, cd and ef in exactly the same manner as described for FIG. 1. In the second, or series, position, the arcuate metallic contacts 17 and 18 are adapted to respectively common the stationary contacts E and H and the stationary contacts F and G, whereby the three 2400 volt winding sections and the two 210 volt winding sections are connected in series to provide a 7620 volt primary in a circuit which may be traced from one power line lead 12, stationary contact A, 2400 volt winding section ab, stationary contact B, 210 volt winding section bh, stationary contact H, arcuate movable contact 17, stationary contact E, 2400 volt winding section ef, stationary contact F, arcuate movable contact 18, stationary contact G, 210 volt winding section gc, stationary contact C, 2400 volt Winding section cd to stationary contact D and the other power line conductor 12. It will be appreciated that the switch of the invention when connected as shown in FIG. 2 is adapted to vary the transformer voltage ratio in the non-integer multiple of 2400 to 7620 volts.

The preferred embodiment of the dualvoltage switch of the invention illustrated in FIGS. 3-11 extends through an aperture 20 in a wall 21 of a distribution transformer tank and is adapted to be secured to the tank wall 21 and is preferably immersed in transformer oil within the tank. A metallic tank bushing 22 has an externally threaded cylindrical body portion 23 adapted to extend through aperture 20 and an outwardly extending circumferential flange 25 disposed against the interior surface of tank wall 21 with a resilient annular gasket 26 compressed therebetween when a hexagonal nut 27 is tightened on the externally threaded body portion 23 .to provide sealing means for aperture 20. An axial bore 30 in bushing 22 widens into a larger diameter portion 31 centrally of the length of bushing 22 and also widens adjacent the outer end of bushing 22 into a still larger diameter cylindrical compartment 32. A switch operating shaft 35 extends through axial bore 30 and is provided with a larger diameter, cylindrical, cap receiving head 36 disposed within compartment 32. A resilient O'ring 38 within the portion 31 of the axial bore hermetically seals between shaft 35 and bushing 22 to prevent leakage of oil from the transformer tank.

A stationary contact carrying member 40 of high mechanical strength, high dielectric strength and high tracking resistance insulating material such as glass filled alkyd resin has an axial bore 41 which receives switch operating shaft 35 and also has a pair of generally radially extending, diametrically opposed arms 43 each of which has four spaced apart, axially extending protrusions 45 on which the switch stationary contacts A-H are mounted. Stationary contact carrying member 40 is contiguous with bushing 22 and has a diametrically extending keyway slot 47 on the outer end thereof which receives a diametrically extending key portion 48 on bushing 22 to prevent rotation of stationary contact carrying member 40. A movable contact carrying member 49, preferably of the same high dielectric and high mechanical strength and high tracking resistance insulating material as member 40, has

an axial bore 50 which receives operating shaft 35 and supports the movable arcuate metallic contacts 17 and 18. A helical compression spring 52 surrounding operating shaft 35 between stationary contact carrying member 40 and movable contact carrying member 49 urges the latter in a direction away from the former, and a camming pin 53 extending transversely through operating shaft 35 adjacent the end thereof limits movement of movable contact carrying member 49 away from member 40 and provides a driving connection between movable contact carrying member 49 and the operating shaft 35 in a manner explained hereinafter.

A switch operating cap 55, which may be of phenolic material, is internally threaded to mate with the external threads on bushing '22 and is normally engaged with bushing 22 with a resilient gasket 56 therebetween to prevent entrance of moisture or dirt which might interfere with switch operation and :also to provide an additional seal against leakage of oil from the transformer tank in the event that gasket 26 or 3 8 became damaged. Cap has a smaller diameter, noncircular, centrally disposed switch actuating boss 58 (see FIG. 7) adapted, when cap 55 is unthreaded from bushing 22 and reversed, to slidably fit into a corresponding noncirc-ular cavity 59 (see FIG. 8) in cap receiving [head 36 on shaft 35 to provide a motion transmitting connection through which operating shaft 35 may be rotated to alter the electrical connections between the arcuate metallic contacts 17 and 18 and the stationary contacts AH. In the illustrated embodiment, the noncircular boss 58 and cavity 59 have an arcuate contour for approximately 250 degrees of their external periphery and an inverted-V configuration for the remainder of the periphery, but it will be appreciated that boss 58 and cavity 59 can he of any noncircular matching periphery to permit the application of the switch actuating boss 58 of cap 55 to the cavity 59 in shaft 35, when cap 55 is removed from its sealing position on bushing 22 and reversed, to effect the motion transmitting connection between cap 55 and shaft 35. A peripheral portion of cap 55 is provided with a .plurality of outwardly extending, circumferentially spaced ribs 60 which facilitate tightening or loosening cap 55 on bushing 22. It will be appreciated that cap 55 selectively provides a sealed closure for the operating mechanism of the dual voltage switch or affords, as an integral part thereof, a switch actuating means by which the position of the switch movable contact may be easily and quickly changed without requiring the use of tools. The majority of distribution transformers are pole mounted, and in order to effect the desired alteration of switch connections, the lineman must usually climb the pole. The disclosed construction affords a simple and effective means by which the external operating portion of the switch is maintained in sealed condition under normal conditions, and its position may be readily altered by removal of cap 55 and the reversal of its position to effect the insertion of noncircular boss 58 in cavity 59 to establish an ope-rating connection between cap 55 and shaft 35. Rotation of cap 55 may then be effected to alter the switch connections within the transformer tank and change the voltage ratio of the transformer.

Means are also provided to insure that capcannot be returned to its normal position in threaded engagement with bushing 22 unless the dual voltage switch is in proper position. As best seen in FIGS. 8 and 9, cap receiving head 36 on shaft 35 is provided with two peripherally spaced, radially extending slots 62 and 63, and bushing 22 is also provided with a radially extending slot 64. The internal periphery of bushing 22 is also provided with an inwardly extending, circumferential groove 66 in which is positioned a pivot pin 67 extending transversely through a latch 68 disposed in radial slot 64 to provide a pivotal connection for latch 68. When radial slot 64 in bushing 22 registers with radial '5 slot 62 in head 36, the movable arcu'ate switch contacts 17 and 18 are in the parallel position, and when radial slot 64 registers with radial slot 63 in head 36, the movable switch contacts 17 and 18 are in the series position. Latch 68 normally occupies a position gene-rally transverse to the axis of shaft 35 and in noncircular cavity 59 and in the registering radial slots 64 and 62, as shown in full lines in FIG. 9, or the registering radial slots 64 and 63, and latch 68 may be actuated to the dotted line position shown in FIG. 9 wherein it is removed from cavity 59 and from radial slot 62 or radial slot 63, and shaft 35 is then free to rotate when noncircular boss 58 on cap 55 is mated with noncircular cavity 59. Boss 58 cannot be inserted into cavity 59 and shaft 35 cannot rotate until latch 68 is removed from radial slot 62 or 63, and if shaft 35- is not rotated sufficiently to move arcuate contacts 17 and 18 into the series or the parallel position, the radial slot 64 will not register with radial slot 62 or 6 3, the latch 68 cannot be pivoted into its normal position within cavity 59, and consequently the raised latch 68 prevents threading cap 55 on bushing 22. It will thus be appreciated that the disclosed construction assures that the switch movable contacts are fully actuated into the series or parallel position and that they are not hung up between switch positions.

Means for preventing rotation of the shaft beyond the series and parallel positions includes a stop 70 on bushing 22 (see FIGS. 9 and 10') extending parallel to the axis of shaft 35 and aflixed to the shoulder 71 formed at the junction of portion 31 and compartment 32 in bushing 22. Stop 70 cooperates with a radially extending arm 73 (see FIG. 10) von head 36 of shaft 53. Arm 73 extends for approximately 110 degrees of the periphery of shaft 35 and hits stop 70 to positively prevent shaft 35 from further rotation after shaft 35 has been rotated approximately 250 degrees in the direction shown by the arrow in FIG. 10 to bring groove 63 in head 36 in register with groove 64 in bushing 22, thereby actuating the movable contacts 17 and 18 to the series position.

Stationary contacts A-H are affixed to the axially extending protrusions 45 on member by screws 75 threaded within the insulating material of stationary contact carrying member 40. Each contact A-H is a gene'rally fiat member of suitable conductive metal suchas copper having an upstanding portion 76 with an arcuate upper surface adapted to be engaged by the movable contacts 17 and 18. An upstanding radially extending guide 77 on each protrusion abuts against a flat side of each stationary contact A-H and prevents the stationary contact from turning relative to the protrusion 45. Circular raised skirts 78 on stationary contact carrying member 40 concentric with shaft 35 substantially increase the creepage distance between the shaft 35 and the stationary contacts A-H.

Movable arcuate contacts 17 and 18 are supported in axially spaced relation to movable contact carrying member 49 by headed screws 80, which extend freely through clearance apertures 81 adjacent the ends of member 49 and are threaded with-in tapped holes in arcuate contacts 17 and 18, and compression springs 82 circumjacent screws 80 between member 49 and the arcuate contacts 17 and 18. Springs 82 are normally loaded to a predetermined force by screws 80, and springs 82 are further compressed to a sufficient extent by cam pin 53 to raise the heads of screws 80 off movable contact carrying member 49 as shown in FIG. 11 when the movable contacts 17 and 18 are in the series and parallel positions, thereby assuring a predetermined mini-mum contact pressure between mova'ble and stationary contacts of the dual voltage switch. Each screw 80 is enclosed within an arcuate housing 84 on movable member 49 in order to increase the creepage distance between shaft 35 and the movable contacts 17 and 18. Generally arcu-ate raised barriers 85 are disposed on movable contact carrying member 49 between the housings 84 and shaft 35 to further increase the creepage distance along the surface of member 49 and to thus increase the breakdown strength of the switch.

A motion transmitting connection is established between operating shaft 35 and movable contact carrying member 49 by the cam pin 53, which extends transversely through the end of shaft 35, in cooperation with a camming surface 87 on movable contact carrying member 49 generally transverse to the axis of shaft 35. Cam pin 53 and cammin-g surface 87 also cooperate to provide high pressure engagement between movable contacts 17, 18 and stationary contacts A-H when the switch in the series and in the parallel position but to relieve the pressure while the switch is being actuated between switch positions and thus minimize the torque required to operate the switch. Camming surface 87 includes two diametrically opposed, flat, arcuate, cam faces 88 (see FIG. 5), each of which covers approximately ninety degrees in a plane transverse to the axis of shaft 35, separated by two generally V-shaped cam faces 89 forming depressions. When cam pin 53 engages the flat cam faces 88, the movable contact carrying member 49 is actuated axially of shaft 35 toward the stationary contact carrying member 40 into the position shown in FIG. 3 wherein the stationary contacts A-H overcome the predetermined force with which springs 82 are loaded and move the heads of screws off member 49, whereby .a predetermined high contact pressure is obtained between stationary and movable contacts. When cam pin 53 falls int-o a depression formed by a V-shaped cam face 89, member 49 is actuated by springs 80 and 52 axially of shaft 35 away from member 40 into the position shown in FIG. 11 wherein contact pressure between stationary contacts A-H and movable contacts 17, 18 is relieved and minimum torque is required to rotate member 49 carrying movable contacts 17 and 18. Shaft 35 is rotated through approximately 250 in actuating the switch between series and parallel positions. During the initial approximately sixty degree rotation of shaft 35, cam pin 53 is moved across part of a flat cam face 88 and onto one sloping side of the V-shaped cam face 89 forming the cam depression. As cam pin 53 is actuated toward the bottom of the cam depression 89, member 49 is moved away from member 40 by springs 52 and 80 to relieve the high contact pressure between movable contacts 17 18 and stationary contacts A-H. A driving connection is established between shaft 35 and member 49 when cam pin 53 falls into the lowest part of the cam depression 89, and further rotation of shaft 35 initiates turning of member 49 carrying movable contacts 17 and 18. If an ex cessive overload has welded the stationary and movable contacts together, movable contact carrying member 49 cannot move in an axial direction away from member 40, and a contact break pin 90 extending through shaft 35 between members 40 and 49 strikes diametrically opposed, radially inward extending arms 91 on movable contact carrying member 49 after cam pin 53 has slid off flat surface 88 and started down the incline of the V-shaped cam face 89, thereby establishing a positive connect-ion between shaft 35 and movable contact carrying member 49 and breaking the weld between movable and stationary contacts upon further rotation of shaft 35. During normal operation of the switch 10, the member 49 is actuated axially a sufficient distance so that contact break pin 90 cannot strike the radial inwardly extending arms 91 as can be seen in FIG. 11. However, if stationary and movable contacts become welded, cam pin 53 slides down the incline of cam face 89 until the heads of bolts 80 engage member 49, at which point cam pin 53 leaves cam surface 89. Contact break pin 90 then strikes arms 91 to break the weld upon further rotation of shaft 35 and permitting cam pin 53 to drop to the bottom of cam surface 89.

Although shaft 35 is rotated approximately 250 degrees in actuating the movable switch contacts 17 and 18 between series and parallel positions, movable contact member 49 is actuated somewhat less than ninety degrees between these positions. Cam pin 53 and shaft 35 rotate approximately ninety degrees before a driving connection is established between shaft 35 and movable contact carrying member 49. Stop means are provided to assure that the movable contacts 17 and 18 have been actuated fully into the series and parallel positions before the contact pressure is increased by actuating movable contact carrying member 49 axially toward stationary contact carrying member 40. Four circumferentially spaced apart, radially extending stop projections 92 (see FIGS. 6 and 11) on stationary contact carrying member 40 are in the path of movement of a pair of diametrically opposed, axially extending stop members 93 on movable contact carrying member 49 and prevent actuation of movable contacts 17 and 18 beyond the series and parallel switch positions. The stop projections 92 and stop members 93 are in interfering relation in both the high contact pressure and the low contact pressure axial positions of member 49.

Assume that the switch is in parallel position with the stop members 93 in the full line position against stop projections 9=2P as shown in FIG. 6. After shaft 35 has been rotated approximately ninety degrees from'its initial position on flat cam face 88, cam pin 53 falls into the bottom of V-shaped cam depression 89 to establish a driving connection between shaft 35 and member 49 and permits springs 52 and 80 to actuate member 49 carrying movable contacts 17 and 18 axially away from member 40 to the position shown in FIG. 11 and release the high contact pressure, whereby movable contact carry ing member 49 can be rotated with minimum torque applied to shaft 35. Continued rotation ofv shaft 3 through somewhat less than ninety degrees will actuate member 49 carrying contacts 17 and 18 from the paralle toward the series position until stop members 93 on member 49 are in the position shown in dotted lines in FIG. 6 and strike the stop projections 928 on member 40, thereby assuring that the contacts 17 and 18 are fully actuated into the series position. Further rotation of shaft 35 causes cam pin 53 to ride up the V-shape cam face 89 (since interference of stop members 928 and 93 prevent member 49 from turning relative to member 40) and onto flat cam face 88 and to actuate movable contact carrying member 49 axially toward stationary contact carrying member 40' against the force of springs 52 and 80 until the heads of screws 80 are moved off member 49, thereby assuring that the desired predetermined high contact pressure is again established between movable contacts 17 and 18 and stationary contacts A-H. In this position noncircu lar boss 58 on cap 55 can be disengaged from cavity 59 and latch 68 can be pivoted downwardly into radial slot 63 and cavity 59, thereby permitting cap 55 to be engaged with the external threads on bushing 22.

While only a single embodiment of the invention has been illustrated and described, many modifications and variations thereof will be readily apparent to those skilled in the art, and consequently it is intended in the appended claims to cover all such modifications and variations which fall within the true spirit and scope of the invention.

I claim:

1. In an electrical switch connected to two current carrying conductors, the combination of two sets of four stationary contacts, means for supporting said stationary contacts, three electrical windings separately connected at their respective ends across three consecutive contacts of each of said two contact sets, the windings respectively connected at one of their ends to the middle contact of the three consecutive contacts of each of said sets being connected at their other ends to an outside contact of the three consecutive contacts of the other of said sets, the two said current carrying conductors separately connected to the middle contact of the three consecutive contacts of each of said contact sets, the fourth contact of each set being separately connected to the most adjacent contact of the same set, said fourth contact of each set being located with respect to the other fourth contact at opposite ends of the said three consecutive contacts of said fourth contacts respective set, said switch having first and second movable conductive members, means for supporting and moving said movable conductive members, said movable conductive members each being respectively adapted in a first position to electrically common the three consecutive contacts of one of said sets, whereby the said windings are connected in parallel, and said conductive members being operable to a second position wherein each said member respectively electrically commons said fourth contacts of one set and the nearest adjacent contact Olf the other set, whereby said windings are connected in series.

2. In the combination defined by claim 1 and including two additional electrical windings one of which connects said fourth contact of said one set and the most adjacent contact of the same set and the other of which connects said fourth contact of the other set and the most adjacent contact of that set, whereby five electrical windings are connected in series when said switch is operated to said second position.

3. In an electrical switch the combination with an inductive apparatus, said switch having stationary contacts connected to a plurality of electrical windings, the combination of eight stationary contacts, means for supporting said stationary contacts, first andsecond movable conductive members, common means for supporting and moving said movable conductive members, said movable conductive members each being adapted when in a first position to electrically common three of said eight station- .ary contacts, and said movable conductive members each being adapted when in a second position to electrically common two of said eight stationary contacts, said movable conductive members and stationary contacts being constructed and arranged to multiply connect those of said electrical windings connected between the stationary contacts commoned by said conductive members when said members are in their first position, and to serially connect all of said electrical windings when said conductive members are in their second position.

4. In an electrical switch having-its stationary contacts connected to a plurality of electrical windings, the combination of eight spaced apart stationary contacts, means for supporting said stationary contacts, the first and fifth stationary contacts being connected to the ends of one of said electrical windings, the second and seventh stationary contacts being connected tothe ends of another of said electrical windings, the third and sixth stationary contacts being connected to the ends of another of said electrical windings, the third and fourth stationary contacts being connected to the ends of another of said electrical windings, the seventh and eight stationary contacts being connected to the ends of another of said electrical windings, first and second elongated metallic members, means for supporting and moving said metallic members, each of said metallic members being adapted in a first position to respectively electrically common said first, second and third contacts and said fifth, sixth and seventh contacts, and each of said metallic members being adapted in a second position to respectively common said first and eighth contacts and said fourth and fifth contacts, said metallic members and stationary contacts being constnucted and arranged when in said first position to multiply connect the electrical windings connected to the first and fifth contacts, second and seventh contacts and third and sixth contacts, and when in said second position to serially connect all electrical windings connected to the stationary contacts.

5. In combination, an electrical switch having a stationary member, eight contacts mounted in spaced apart relation in a circle on said stationary member, a first winding connected at its ends to the first and fifth contacts, a second winding connected at its ends to the second and seventh contacts, a third winding connected at its ends to the third and sixth contacts, means for electrically interconnecting the third and fourth contacts, means for electrically interconnecting the seventh and eighth contacts, said switch having a movable member means for supporting said morvabl'e member, first and second elongated metallic members mounted on said movable member, said movable member being rotatable relating to said stationary member about an axis through the center of said circle from a first position wherein said first and second metallic members respectively electrically common said first, second and third contacts and said fourth, fifth and sixth contacts, whereby said first, second and third windings are connected in parallel, and a second position wherein said first and second metallic members respectively electrically common said first and eighth contacts and said fourth and fifth contacts, whereby said first, second and third windings and both of said interconnecting means, are connected in series.

6. In combination, an electrical switch having a stationary member, eight contacts mounted in spaced apart relation in a circle on said stationary member, the third and fourth contacts being electrically connected and the seventh and eight contacts being electrically connected, a first winding connected at its ends to the first and fifth contacts, a second winding connected at its ends to the second and seventh contacts, a third winding connected at its ends to the third and sixth contacts, said switch having an axially actuable movable member carrying first and second elongated metallic members and being rotatable relative to said stationary member about an axis through the center of said circle from a first position wherein said first and second elongated metallic members respectively electrically common said first, second and third contacts and said fourth, fifth and sixth contacts, where-by said first, second and third windings are in parallel, and a second position wherein said first and second elongated metallic members respectively electrically common said first and eighth contacts and said fourth and fifth contacts, whereby said first, second and third windings are in series, means including a stopprojection on said stationary member cooperating with a stop portion on said movable member for preventing rotation of said movable member beyond said first and second positions, spring means for urging said movable member axially away from said stationary member, and means for actuating said movable member axially toward said stationary member against the force of said spring means when said movable member is in said first and second positions to provide high contact pressure between said contacts and said elongated metallic members and 'for actuating said movable member axially away from said stationary member when said movable member is being operated between said first and second positions.

7. An electrical switch comprising, in combination, a stationary member, a plurality of spaced apart stationary contacts mounted in an arc on said stationary member, an operating shaft rotatable about an axis through the center of said are, a movable member rotatable about said axis and being displacea ble axially toward and away from said stationary member, a metallic contact carried on said movable member and being movable relative to said movable member parallel to said axis and adapted to engage said stationary contacts, spring means for resiliently loading said metallic contact against movement toward said movable member, said movable member being rotatable between a first position wherein said metallic contact electrically commons a first set of said stationary contacts and a second position wherein it electrically commons a different set of said stationary contacts, means including a camming surface on said movable member and a cam pin through said shaft for establishing a driving connection between said movable member and said shaft and for actuating said movable member axially toward said stationary member, to overcome the force of said spring means, when said movable member carrying said metallic contact is at rest in said first and second positions and for actuating said movable member axially away from said stationary member when said movable member carrying said metallic contact is being actuated between said first and second positions, and a contact break pin through said shaft adapted to strike and rotate said movable member when said driving connection between said cam pin and said camming surface is ineffectual in rotating said movable member carrying said metallic contact between said first and second positions.

8. An electrical switch comprising, in combination, a stationary member, a plurality of stationary contacts mounted in spaced apart relation in a circle on said stationary member, an operating shaft rotatable about an axis through the center of said circle, a rotatable member coaxial with said shaft and being displaceable axially toward and away from said stationary member, a metallic contact carried on and being movable relative to said rotatable member parallel to said axis, resilient means for urging said metallic contact in a direction away from said rotatable member, means for holding said metallic contact in a position relative to said rotatable member wherein said resilient means are loaded to a predetermined force, means including a camming surface on said rotatable member and a cam pin through said shaft cooperating with said cam-ming surface for establishing a driving connection between said shaft and said rotatable member and for rotating said rotatable member between a first position wherein said metallic contact electrically commons a first set of said stationary contacts and a second position wherein it electrically commons a different set of said stationary contacts, cooperating members on said stationary and rotatable members for preventing operation of said rotatable member carrying said metallic contact beyond said first and second positions, said camming surface and said cam pin displacing said rotatable member toward said stationary member against the force of said resilient means when said rotatable member is at rest with said metallic contact in said first and second positions, and a contact break pin through said shaft adapted to strike and rotate said rotatable member when said resilient means cannot displace said rotatable member axially away from said stationary member and said driving connection is ineffectual in rotating said rotatable member between said first and second positions.

9. An electrical switch comprising, in combination, a rotatable member having a camming surface generally transverse to its axis of rotation and provided with a depression therein, a radially extending projection on said rotatable member, a stop on said rotatable member extending parallel to the axis thereof, a metallic contact carried by and movable relative to said rotatable member parallel to said axis, means including springs disposed between said rotatable member and said metallic contact for resiliently urging said metallic contact in an axial direction away from said rotatable member with a predetermined force, a stationary member coaxial with said rotatable member, a plurality of stationary contacts mounted in spaced apart relation on said stationary member about an are having said axis on its center and opposite said metallic contact on said rotatable member, an operating shaft coaxial with said stationary and rotatable members, a cam pin through said shaft in engagement with said camming surface and urging said metallic contact with sufficient force against said stationary contacts to compress said springs, said cam pin being rotatable into said depression to establish a driving connection between said shaft and said rotatable member and permitting said rotatable member to be displaced under the force of said springs axially away from said stationary member, said rotatable member being rotatable through said driving connection to actuate said metallic contact between a first position wherein it electrically commons one set of said stationary contacts and a second position wherein it electrically commons a different set of said stationary contacts, radially extending stop means on said stationary member cooperating with said stop on said rotatable member to prevent operation of said rotatable member beyond said first and second positions, and a contact break pin through said shaft cooperating with said radial projection on said rotatable member to establish a positive connection between said shaft and said rotatable member when said springs cannot move said rotatable member axially away from said stationary member and said driving connection is ineffectual to operate said rotatable member between said first and second positions.

10. In an electrical switch having a plurality of stationary contacts arranged in a circle and a movable contact rotatable into engagement with saidstationary contacts and operable axially to vary the contact pressure therebetween and wherein a driving connection is established between said movable contact and a switch operating shaft by a cam pin on said shaft in engagement with a depression in a camming surface on said movable contact and said cam pin and camming surface control axial movement of said movable contact toward and away from said stationary contacts, the improvement of a projection on said movable contact and a contact break pin on said shaft adapted to strike said projection and actuate said movable contact when said movable contact cannot move axially and said driving connection is ineffectual in rotating said movable contact.v

11. An electrical switch including a rotatable member having a camming surface generally transverse to its axis of rotation and a depression in said camming surface and also having a stop portion and a contact break portion, a stationary member coaxial with said rotatable member and having stop means cooperating with said stop portion to limit operation of said rotatable member beyond first and second positions, a plurality of stationary contacts mounted in spaced apart relation in an are on said stationary member, a metallic contact on said rotatable member engaging said stationary contacts and electrically commoning a first set of said stationary contacts when said rotatable member is in said first position and a different set of said stationary contacts when said rotatable member is in said second position, an operating shaft coaxial with said stationary and rotatable members, a cam pin through said shaft in engagement with said camming surface and cooperating therewith to displace said rotatable member toward and away from said stationary member When said rotatable member is at rest in said first and second positions, whereby contact pressure between said stationary contacts and said metallic contact is varied, and also establishing a driving connection between said rotatable member and said shaft when said cam pin is in said depression, and a contact break pin through said shaft cooperating with said contact break portion to strike and operate said rotatable member when said rotatable member is held against axial movement and said driving connection is ineffectual to rotate said rotatable member.

12. A compact electrical switch adapted to extend through an opening in a casing wall and be mounted on said wall comprising, in combination, a generally cylindrical bushing member having a threaded portion extending through said opening and a circumferential flange disposed adjacent said casing wall and being provided with an axial bore, a nut engaging said threaded portion and disposed adjacent the opposite side of said casing wall from said flange and afilxing said bushing to said casing wall, an operating shaft extending through said axial bore, a stationary insulating member disposed against the portion of said bushing interior of said casing and having an axial bore receiving said shaft, means for preventing rotation of said stationary member relative to said bushing, a plurality of stationary contacts mounted on said stationary member in spaced apart relation in a circle having the axis of said shaft as a center, a movable insulating member having an axial bore receiving said shaft and being disposed adjacent said stationary member and being displaceable axially relative to said stationary member and having a camming surface transverse to the axis of said shaft provided with a depression therein, an elongated metallic movable contact carried on said movable member and adapted to engage said stationary contacts, a cam pin through said shaft in engagement with said camming surface, said cam pin cooperating with said camming surface to establish a driving connection between said shaft and said movable member permitting rotation of said movable member between first and second positions wherein said movable contact electrically commons different sets of said stationary contacts and also cooperating to displace said movable member axially toward and away from said stationary member to vary the contact pressure between said stationary and movable contacts when said movable member is at rest in said first and second positions.

13. An electrical switch comprising, in combination, a plurality of spaced apart stationary contacts mounted in a circle, a movable contact rotatable about an axis through the center of said circle between first and second positions wherein it engages different sets of said stationary contacts and being displaceable axially toward and away from said stationary contacts to vary the contact pressure therebetween and having a camming surface with a depression therein, an operating shaft coaxial with said movable contact, stop means for preventing rotation of said movable contact beyond said first and second positions, a cam pin on said shaft cooperating with said camming surface to actuate said movable contact toward and away from said stationary contacts when it is at rest in said first and second positions and establishing a driving connection between said shaft and said movable contact when said cam pin falls into said depression, a contact break projection on said movable contact, and a contact break pin on said shaft adapted to strike said contact break projection and rotate said movable contact if said movable contact is undesirably held against axial displacement and said driving connection is ineffectual to rotate said movable contact.

14. A compact electrical switch adapted to extend through an opening in a casing wall and be mounted on said wall, comprising, in combination, a generally cylindrical bushing member extending through said opening and having an axial bore and an axial compartment of larger diameter than said bore, means for affixing said bushing so extending through said opening on said casing wall and for hermetically sealing therebetween, a stationary insulating member coaxial with and disposed against the portion of said bushing interior of said casing and having an axial bore, a plurality of stationary metallic contacts mounted in spaced apart relation on said stationary member in a circle having the axis of said shaft as the center, means for preventing rotation of said stationary member relative to said bushing, a movable insulating member disposed adjacent against said stationary member and being axially displaceable relative thereto and having an axial bore and a camming surface transverse to the axis thereof having a depression therein, an elongated metallic movable contact, means including springs for carrying said movable contact on said movable member and for resiliently urging it toward movement away from said movable member and toward said stationary contacts, an operating shaft extending through the axial bores in said bushing, said stationary member, and said movable member and having a larger diameter head portion disposed within said axial compartment, a cam pin through said shaft in engagement with said camming surface, said cam pin cooperating with said camming surface to establish a driving connection between said shaft and said movable member permitting rotation of said movable member between first and second positions wherein said movable contact electrically commons different sets of said stationary contacts, and cooperating members on said stationary and movable members for preventing rotation of said movable member beyond said first and second positions, said cam pin and said camming surface also cooperating to displace said movable member axially toward said stationary member to compress said springs and increase the pressure between said stationary and movable contacts when said movable member is at rest in said first and second positions and permitting displacement of said movable member axially away from said stationary member by said springs to relieve said contact pressure when said movable member is being rotated between said first and second positions.

15. A compact electrical switch adapted to extend through an opening in a casing wall and be mounted on said wall comprising, in combination, a stationary insulating member having an axial bore, means for mounting said stationary member on said casing wall so that said axial bore is in register with said opening and for preventing rotation of said stationary member, an operating shaft extending through said axial bore, a movable insulating member rotatably carried on and being displaceable axially of said shaft and having a camming surface transverse to the axis of said shaft provided with a depression, a plurality of stationary metallic contact members mounted in spaced apart relation on said insulating member in a circle having said axis as its center, a metallic elongated movable contact carried on said movable member and adapted to engage said stationary contacts, spring means for increasing contact pressure between said stationary and said movable contacts when said movable member is displaced axially toward said stationary member, a cam pin through said shaft engaging said camming surface and cooperating therewith to establish a driving connection between said shaft and said movable member when said pin falls into said depression and permitting rotation of said movable member between first and second positions wherein said movable contact electrically commons different sets of said stationary contacts, and stop members on said stationary and movable members preventing rotation of said movable member beyond said first and second positions, said cam pin and camming surface also cooperating to displace said movable member axially toward said stationary member when it is at rest in said first and second positions and to displace it axially away from said stationary member before it is rotated between said first and second positions.

References Cited by the Examiner UNITED STATES PATENTS 3,066,208 11/1962 Fannon et al. 3,177,305 4/1965 Lehman 200-6 ROBERT K. SCHAEFER, Primary Examiner.

I. R. SCOTT, Assistant Examiner. 

1. IN AN ELECTRICAL SWITCH CONNECTED TO TWO CURRENT CARRYING CONDUCTORS, THE COMBINATION OF TWO SETS OF FOUR STATIONARY CONTACTS, MEANS FOR SUPPORTING SAID STATIONARY CONTACTS, THREE ELECTRICAL WINDINGS SEPARATELY CONNECTED AT THEIR RESPECTIVE ENDS ACROSS THREE CONSECUTIVE CONTACTS OF EACH OF SAID TWO CONTACT SETS, THE WINDINGS RESPECTIVELY CONNECTED AT ONE OF THEIR ENDS TO THE MIDDLE CONTACT OF THE THREE CONSECUTIVE CONTACTS OF EACH OF SAID SETS BEING CONNECTED AT THEIR OTHER ENDS TO AN OUTSIDE CONTACT OF THE THREE CONSECTIVE CONTACTS OF THE OTHER OF SAID SETS, THE TWO SAID CURRENT CARRYING CONDUCTORS SEPARATELY CONNECTED TO THE MIDDLE CONTACT OF THE THREE CONSECUTIVE CONTACTS OF EACH OF SAID CONTACT SETS, THE FOURTH CONTACT OF EACH SET BEING SEPARATELY CONNECTED TO THE MOST ADJACENT CONTACT OF THE SAME SET, SAID FOURTH CONTACT OF EACH SET BEING LOCATED WITH RESPECT TO THE OTHER FOURTH CONTACT AT OPPOSITE ENDS OF THE SAID THREE CONSECUTIVE CONTACTS OF SAID FOURTH CONTACT''S RESPECTIVE SET, SAID SWITCH HAVING FIRST AND SECOND MOVABLE CONDUCTIVE MEMBERS, MEANS FOR SUPPORTING AND MOVING SAID MOVABLE CONDUCTIVE MEMBERS, SAID MOVABLE CONDUCTIVE MEMBERS EACH BEING RESPECTIVELY ADAPTED IN A FIRST POSITION TO ELECTRICALLY COMMON THE THREE CONSECUTIVE CONTACTS OF ONE OF SAID SETS, WHEREBY THE SAID WINDINGS ARE CONNECTED IN PARALLEL, AND SAID CONDUCTIVE MEMBERS BEING OPERABLE TO A SECOND POSITION WHEREIN EACH SAID MEMBER RESPECTIVELY ELECTRICALLY COMMONS SAID FOURTH CONTACTS OF ONE SET AND THE NEARESET ADJACENT CONTACT OF THE OTHER SET, WHEREBY SAID WINDINGS ARE CONNECTED IN SERIES. 